Instead, at his urging, the next incoming class of new students at Tennessee Virtual Academy won't be admitted — an action that has nevertheless put an education chief known for favoring school choice under unfamiliar fire from national reform groups.

The move to "un-enroll" 626 incoming students marks the boldest action yet in what has been a turbulent three years for the online virtual school operated by the for-profit K12 Inc., which has produced woeful test scores every year in Tennessee since a change in law paved the way for its 2011 arrival.

Because of the school's third straight year of "Level 1" results in student growth, the commissioner had the authority to direct the closure of the school. He chose a less harsh option, recommending that the Union County School Board, which contracts K12 to operate in Tennessee, stop admitting students for the time being.

The board obliged on Thursday, voting to request a waiver from the state to cancel enrollment of students it recently accepted. Tennessee Virtual Academy's some 3,000 existing students, who live across the state and take coursework from home, will remain part of the school.

Why not close it outright? Huffman noted Tennessee Virtual Academy students have shown improvement in years two and three, and that challenges rest primarily with first-year students.

"We definitely considered it, but we wanted to take a deeper look at the data, and when you take a deeper look at the data, you see that the students who have been there two years or three years perform at a reasonable level," Huffman told The Tennessean on Friday.

Moving forward, he said, "They need to show better results and have a plan also for how they're going to on-board new students and ensure that students who they're enrolling are students who can succeed."

Tennessee Virtual Academy, made possible by a 2011 law, has challenged Gov. Bill Haslam's administration from the outset, quickly becoming an easy punching bag for Democrats and other critics.

Virtual education could be at a crossroads in this state. Tennessee's Virtual Public Schools Act is set to sunset next June, meaning the state legislature will review the merits of the law during the next session.

Though the school will remain open for now, parents and other supporters of Tennessee Virtual Academy aren't happy with the outcome.

Nearly 1,200 people as of late Friday had signed an online petition asking that the Union County board not cancel the enrollment of the more than 600 students.

"Our country's educational system is in the midst of a technological revolution," the petition reads. "We are making history by utilizing virtual schooling. The fact that there are challenges in the virtual system isn't a surprise."

Other groups weighed in as well. The Tennessee chapter of PublicSchoolOptions.orgcalled for an "immediate meeting" on Monday between parents of the school and Huffman and Haslam — a request Huffman told The Tennessean he hadn't seen.

The Washington, D.C.-based Center for Education Reform issued a statement saying it "strongly condemns" the directive of Huffman. "It's an outrage that these 626 legally enrolled students are now being forcefully turned away, just two weeks before the start of the school year," said Kara Kerwin, the organization's president.

In slowing down the growth of the Tennessee Virtual Academy, Huffman has had to take aim at an option he has supported exploring. In addition to low test marks, the school has also had high attrition, meaning kids have often gone back to their local districts with low proficiency marks.

"I believe that it's important to try things like virtual education," he said. "That's why, at some level, it's been disappointing to me to see the results."

As for the Union County school system, Huffman called it "irresponsible" and "disappointing" for it to initially admit a class of 626 students for this fall, alleging the board was alerted of its "Level 1 status" on June 15. Results from the 2013-14 Tennessee Comprehensive Assessment Program for individual districts are to be publicly released next week.

Union County officials initially balked at following Huffman's directive, suggesting that it didn't have the legal authority to do so and that it lacked the data Huffman was reviewing. In a follow-up letter Friday after the board's action, Union County Director of Schools James Carter told the commissioner that "we are willing to acknowledge your recommendation," though they still weren't privy to the analysis of data.